Antimicrobial N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]-alkanamines and acid addition salts thereof and methods of use and compositions thereof

Abstract

N-[1-alkyl or arylmethyl)-4(1H)-pyridinylidine]-alkanamine and pharmaceutically acceptable acid addition salts thereof, for example, N-(1-octyl-4(1H)-pyridinylidine)-octanamine monohydrochloride salt, which are useful as antimicrobial agents, especially on living tissues and nonliving surfaces and most especially against pathogenic dental microbes, and a process for perparation, methods of use and compositions thereof are disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my copending application Ser. No. 649,587 filed Sept. 12, 1984, now U.S. Pat. No. 4,598,082, issued July 1, 1986.

BACKGROUND OF THE INVENTION

PAC Field of the Invention

The invention relates to N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamines and acid addition salts thereof, which are useful as antimicrobial agents, especially on living tissues and nonliving surfaces and most especially against pathogenic dental microbes, and a process for preparation, methods of use and compositions thereof.

Information Disclosure Statement

Landquist (Journal of the Chemical Society, Perkin Transactions I, no. 4, pp. 454-456, 1976) describes the preparation of 1-methyl-4-methylaminopyridinium iodide and 4-dodecylamino-1-methylpyridinium iodide but does not describe or suggest any biological property thereof.

Bailey U.S. Pat. No. 4,206,215 issued June 3, 1980 describes antimicrobial bis[4-(substituted-amino)-1-pyridinium]alkane salts having the structural formula ##STR1## wherein: Y is an alkylene group containing from 4 to 18 carbon atoms and separating the two 4-(R-NH)-1-pyridinyl groups by from 4 to 18 carbon atoms;

R is an alkyl group containing from 6 to 18 carbon atoms, a cycloalkyl group containing from 5 to 7 carbon atoms, benzyl, or phenyl substituted by methylenedioxy or one or two substituents selected from the group consisting of halogen, lower-alkyl, lower-alkoxy, nitro, cyano and trifluoromethyl;

R₁ is hydrogen or lower alkyl

A is an anion;

m is 1 or 3;

n is 1 or 2;

x is 1, 2 or 3; and

wherein

(m)(2)=(n)(x)

Parts A and B of Example 10 of this patent describe 1,10-bis[4-(octylamino)-1-pyridinium]decane dichloride, which can also be named N,N'-(1,10-decanediyldi-1(4H)-pyridinyl-4-ylidene)bis[1-octanamine]dihydro chloride, and whose generic name is octenidine hydrochloride.

SUMMARY OF THE INVENTION

In a first composition of matter aspect the invention is N-[1-(alkyl or arylmethyl)-4(1H)-pyridylidine]alkanamine having the structural formula ##STR2## wherein R is alkyl having from 6 to 18 carbon atoms; and

R' is alkyl having from 2 to 12 carbon atoms, phenylmethyl or halophenylmethyl; or

an acid addition salt thereof.

A particularly preferred composition of matter aspect of the invention is the compound of Formula I wherein R and R' are both octyl or a pharmaceutically acceptable acid addition salt thereof, which is the compound of Example 1 described below.

The compounds of Formula I and the acid addition salts thereof are useful as antimicrobial agents, especially on living tissues or nonliving surfaces and most especially against pathogenic dental microbes in primates.

In a first process aspect the invention is the method of reducing the number of microbes on a living tissue or a nonliving surface which comprises applying to the tissue or surface an antimicrobially effective amount of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine having the structural formula ##STR3## wherein R is alkyl having from 6 to 18 carbon atoms; and

R" is alkyl having from 1 to 12 carbon atoms, phenylmethyl or halophenylmethyl; or

an acid addition salt thereof.

In a second process aspect the invention is the process of preparing N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidene]alkanamine of Formula II or an acid addition salt thereof which comprises alkylating the corresponding 4-alkylaminopyridine having the structural formula ##STR4## with the corresponding compound having the structural formula

R"-X

Formula IV

wherein X is a displaceable leaving group and isolating the HX acid addition salt, or if the acid addition salt is desired to be that of an acid other than HX isolating the desired acid addition salt by ion exchange, or isolating the free base or a mixture of the free base and the acid addition salt.

In a third process aspect the invention is the method of reducing the number of pathogenic dental microbes and associated dental plaque and gingivitis in a primate which comprises applying to the oral cavity of the primate an antimicrobially effective amount of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine of Formula II or a pharmaceutically acceptable acid addition salt thereof.

In a second composition of matter aspect the invention is an antimicrobial composition which comprises an antimicrobially effective concentration of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine of Formula II or a pharmaceutically acceptable acid addition salt thereof and a compatible vehicle consisting of a diluent and one or more pharmaceutical adjuncts.

DETAILED DESCRIPTION OF THE INVENTION INCLUSIVE OF THE PREFERRED EMBODIMENTS

PAC Definitions of the Variables

In the second process aspect of the invention "corresponding" means that R of Formula II and R of Formula III are the same and R" of Formula II and R" of Formula IV are the same.

R of Formulas I, II and III, which is alkyl having from 6 to 18 carbon atoms, is preferably primary alkyl, can be branched or unbranched, and is for example hexyl, heptyl, octyl, nonyl, dodecyl, tetradecyl, octadecyl or 2-ethylhexyl. Octyl is most preferred.

When R' of Formula I is alkyl of 2 to 12 carbon atoms, it is preferably primary alkyl, can be branched or unbranched, and is for example ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, dodecyl or 2-ethylhexyl. Octyl is most preferred. The preferences for R" of Formulas II and IV, which is alkyl of 1 to 12 carbon atoms, are the same except that it additionally includes methyl.

When R' of Formula I or R" of Formulas II and IV is halophenylmethyl, halo is fluoro, chloro, bromo or iodo. p-Halophenylmethyl is preferred. p-Chlorophenylmethyl is most preferred.

The acid addition salt of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine of Formula I or II can be that of any organic or inorganic acid which does not interfere with the antimicrobial effectiveness of the free base and has the structural formula ##STR5## wherein A is an anion and x is the valence of the anion. Pharmaceutically acceptable acid addition salts are of course necessary in carrying out the pharmaceutical aspects of the invention.

The anion A^x- is, for example, chloride, bromide, iodide, fluoride, sulfate, phosphate, monofluorophosphate, nitrate, sulfamate, methanesulfonate, ethanesulfonate, benzenesulfonate, p-toluenesulfonate, naphthalenesulfonate, cyclohexylsulfonate, naphthalenedisulfonate, cyclohexylsulfamate, acetate, trifluoroacetate, malate, fumarate, succinate, tartrate, tartronate, oxalate, citrate, lactate, gluconate, ascorbate, phthalate, salicylate, benzoate, picrate, methanephosphate, ethane-1-hydroxy-1,1-diphosphonate, thiosulfate, perchlorate, sarcosinate, N-lauroylsarcosinate, nitrilotriacetate, 2-hydroxyethylnitrilodiacetate, zinc phenolsulfonate, 1-oxo-2-pyridinethiolate, tetrafluoroborate, hexachloroplatinate, hexafluoroaluminate, tetrachloroaluminate, hexafluorostannate, hexafluorosilicate, fluorozirconate, laurylsulfate and saccharinate. Chloride, bromide and iodide are preferred. Chloride is most preferred.

The valence x of the anion X^x- is most generally 1, 2 or 3. When A^x- is chloride, for example, x is 1. When A^x- is sulfate, for example, x is 2. When A^x- is phosphate, for example, x is 3.

The displaceable leaving group X of R"-X of Formula IV generally has anionic character and may be the same as A and thus become the same as A^x- after displacement. Chloride, bromide, iodide and readily available sulfonate ester groups, for example, methanesulfonate and p-toluenesulfonate are preferred. Chloride is most preferred.

Preparation of the Compounds

The synthetic intermediates of Formulas III and IV are known classes of compounds and are commercially available or can be made by methods specifically or generally described in the chemical literature. Those compounds of Formula III which are not commercially available can be made by heating at 200°-250°C 4-chloropyridine or an acid addition salt thereof, especially the hydrochloride salt, with the corresponding alkylamine (RNH₂) or an acid addition salt thereof, especially the hydrochloride salt, and isolating the free base form of the product. The preferred compounds of Formula IV wherein X is chloro, bromo or iodo are generally commercially available.

Alkylation of the compounds of Formula III with the compounds of Formula IV is carried out with or without a solvent at a temperature in the range of 40°-250°C The solvent can be any solvent or mixture of solvents which does not interfere with the alkylation and can be selected from the hydrocarbons, halohydrocarbons, alcohols, esters, amides, nitriles and other monofunctional solvents and the polyfunctional and mixed functional solvents. On small scale alkylation without a solvent is preferred. On large scale a solvent is necessary because the reaction is exothermic. The preferred solvent is isooctane (2,2,4-trimethylpentane).

It is generally preferred that the alkylation of the compound of Formula III with the compound of Formula IV produce the desired acid addition salt of the compound of Formula II directly, that is, that X of Formula IV be chosen so that X is the same as A of Formula V. The product of the alkylation is thus the acid addition salt of the free base form of the compound of Formula II with the acid HX. Those compounds of Formula V wherein A cannot be the same as X, that is, wherein A is not a displaceable leaving group and which therefore cannot be prepared by the alkylation process, can be prepared by known ion exchange methods, for example, by use of ion exchange resins or double displacement reactions.

The free base forms of the compounds of Formula II are preferably not isolated because they are difficult to separate from, and less stable than, the acid addition salt forms. Moreover, the acid addition salt forms are generally more desirable for pharmaceutical purposes.

The acid addition salt forms of the compounds of Formulas I and II, that is, the compounds of Formula V, are generally crystalline solids and are purified by recrystallization from appropriate solvents.

In the examples set forth below structures of products are inferred from structures of starting materials and expected courses of preparative reactions. Structural confirmation and estimation of purity of starting materials and products are measured by melting temperature range (m.r.), elemental analysis, infrared (IR) spectral analysis, ultraviolet (UV) spectral analysis, nuclear magnetic resonance (NMR) spectral analysis, gas chromatography (GC), high pressure liquid chromatography (HPLC) and thin layer chromatography (TLC).

Table I sets forth the melting ranges of the compounds of Formula III prepared by the method described above and used in the examples.

TABLE I
______________________________________
##STR6##
R                    m.r. (°C.)
______________________________________
CH3 (CH2)5
63-65
CH3 (CH2)6
43-45
CH3 (CH2)7
58-61
CH3 (CH2)8
53-56
CH3 (CH2)3 (CH3 CH2)CHCH2
oil
CH3 (CH2)11
78-82
______________________________________

EXAMPLE 1

A. A mixture of 4-octylaminopyridine (10 g., 0.048 mole) and octyl bromide (8 ml., 0.048 mole) was heated at 125°C for 8 hr. on one day and for 4 more hr. on the next day. The resulting solid was slurried, first in ether, then in ether-tetrahydrofuran (2:1) and finally in tetrahydrofuran, collected by filtration, washed with ether on the filter, and dried (70°C, 0.1 mm.) affording N-(1-octyl-4(1H)-pyridinylidene)octanamine monohydrobromide (11.95 g., 83% yield, m.r. 108°-112°C), which is the monohydrobromide salt of the compound of Formula I wherein both R and R' are octyl.

B. A mixture of 4-octylaminopyridine (25 g., 0.121 mole) and octyl chloride (20.5 ml., 0.121 mole) was heated at 180°C for 1 hr. More octyl chloride (0.5 ml.) was added and the mixture was again heated at 180°C for 1 hr., then dissolved in dichloromethane. The dichloromethane solution was treated with charcoal, filtered, and stripped of solvent under vacuum. The solid residue was slurried in ether (1.5 kg.), collected by filtration, washed with ether (500 g.), isolated in a dry bag, and dried (50°-80°C, 0.1 mm.). The procedure was repeated using the same amounts of starting materials and the product were combined, affording N-(1-octyl-4(1H)-pyridinylidene)octanamine monohydrochloride (80.5 g., 93% yield, m.r. 120°-125°C), which is the monohydrochloride salt of the compound of Formula I wherein R and R' are both octyl.

C. Octyl chloride (800 ml., 4.70 mole) was added to a solution of 4-octylaminopyridine (650 g., 3.16 mole) in warm (50°C) isooctane (b.p. 99.3°C). The resulting solution was heated under reflux. Crystals began to separate from the solution after 2 hr. Refluxing was continued for 36 hr. The solution was then allowed to cool to room temperature and filtered. The solid was washed with cold cyclohexane (1 l.) then slurried in hot (70°C) cyclohexane (4 l.) for 0.5 hr. The slurry was allowed to cool to 60°C and filtered. The solid (1050 g.) was slurried in boiling cyclohexane for 0.5 hr. The slurry was cooled to 50°C and filtered. The solid was dried at 60°C under vacuum, affording N-(1-octyl-4(1H)-pyridinylidine)octanamine monohydrochloride (1035 g., 92% yield, m.r. 140°-142°C), which is a higher melting crystalline form of the product of part B of this example.

D. A filtered solution of N-(1-octyl-4(1H)-pyridinylidine)-octanamine monohydrochloride salt (33.5 g.) in methanol (335 ml.) was added dropwise with stirring to a filtered solution of saccharin sodium salt (20.1 g.) in water (2.5 l.). The mixture was stirred for several hours, allowed to stand overnight and filtered. The resulting solid was washed with water, and dried, first on the filter and then at 30°-35°C under high vacuum using a dry ice condenser, affording N-(1-octyl-4(1H)-pyridinylidine)octanamine monosaccharin salt (42.2 g., m.r. 65°-67°C).

EXAMPLES 2-24

Examples 2-24 are summarized in Tables II and III. Table II shows the structural formulas of the products. Table III shows the reaction temperatures and yields and melting ranges of the products. When the reaction temperature was 125°C or 130°C, the reaction time was about 12 hr. When the reaction temperature was 180°C, the reaction time was 1-3 hr. In all but Example 6, wherein the solvent was isoamyl alcohol, and Example 19, wherein the solvent was excess methyl iodide, the alkylations were carried out without solvent.

The compound of Example 19 is considered to be identical with the compound described as 4-dodecylamino-1-methylpyridinium iodide and as having been prepared from 4-cyano-1-methylpyridinium iodide and dodecylamine (m.r. 122°-124°C) by the above-cited Landquist reference.

The compounds of Examples 20-24 were purified by first converting the crude hydrochloride salts into the saccharin salts, which are less hygroscopic and more easily recrystallized than the hydrochloride salts. Saccharin sodium salt and methanol solvent were used for the conversion. After recrystallization from methanol the saccharin salts were reconverted into the hydrochloride salts using an ion exchange resin (Amberlite IRA-400, 20-40 ml. of dry resin/g. of saccharin salt) in the chloride ion form and methanol as the eluant. The products crystallized upon removal from methanol from the eluates, and the crystals were washed with ether and dried.

TABLE II
__________________________________________________________________________
##STR7##
Example
R              R"             X
__________________________________________________________________________
2   CH3 (CH2)6
CH3 (CH2)6
Br
3   CH3 (CH2)8
CH3 (CH2)8
Cl
4   CH3 (CH2)7
CH3 (CH2)6
Br
5   CH3 (CH2)7
CH3 (CH2)8
Cl
6   CH3 (CH2)5
CH3 (CH2)5
Bra
7   CH3 (CH2)7
CH3 (CH2)3 (CH3 CH2)CHCH
2              Br
8   CH3 (CH2)3 (CH3 CH2)CHCH2
CH3 (CH2)7
Br
9   CH3 (CH2)6
CH3 (CH2)8
Cl
10   CH3 (CH2)7
CH3 (CH2)5
Br
11   CH3 (CH2)8
CH3 (CH2)6
Br
12   CH3 (CH2)8
CH3 (CH2)7
Br
13   CH3 (CH2)3 (CH3 CH2)CHCH2
CH3 (CH2)3 (CH3 CH2)CHCH
2              Br
14   CH3 (CH2)6
CH3 (CH2)7
Br
15   CH3 (CH2)7
C6 H5 CH2
Cl
16   CH3 (CH2)11
C6 H5 CH2
Cl
17   CH3 (CH2)13
C6 H5 CH2
Cl
18   CH3 (CH2)7
4-ClC6 H4 CH2
Cl
19   CH3 (CH2)11
CH3       I
20   CH3 (CH2)5
CH3 (CH2)6
Cl
21   CH3 (CH2)5
CH3 (CH2)7
Cl
22   CH3 (CH2)5
CH3 (CH2)8
Cl
23   CH3 (CH2)6
CH3 (CH2)5
Cl
24   CH3 (CH2)8
CH3 (CH2)5
Cl
__________________________________________________________________________
a 2/3 HBr salt. HBr salt partly neutralized during workup.

TABLE III
______________________________________
Reaction               Melting
Temperature    Yield   Range
Example  °C.     %       °C.
______________________________________
2        125            76      88-90
3        125            25      140-143
4        125            81      80-81
5        125            81      142-144
6         132a
52      74-76
7        130            94      162-170
8        130            86      115-119
9        130            37      122
10       180            92      78-80
11       180            93       98-101
12       180            92      110-112
13       180            81      152-158
14       180            88       99-101
15       180            85      129-130
16       180            80       99-102
17       180            91      103-108
18       180            43      115-119
19         43b
88      117-121
20       180            64      75-78
21       180            38      91-94
22       180            70      112-114
23       180            71      70-76
24       180            79      104-106
______________________________________
a Isoamyl alcohol solvent. Refluxed overnight.
b Excess methyl iodide solvent. Refluxed overnight.

Antimicrobial Properties of the Compounds

As stated above and in accordance with the first process aspect of the invention the compounds of Formulas I and II and the acid addition salts thereof are useful as antimicrobial agents, especially on living tissues or nonliving surfaces. This was demonstrated in the excised porcine skin disk immersion test against both resident and transient microflora.

In the test against resident microflora sterile excised porcine skin disks 10 mm. in diameter were inoculated with a Klebsiella oxytoca K-1 (Bender Hygienic Laboratory, Albany, N.Y.) or Staphylococcus epidermidis ATCC 17917 culture containing between 10⁶ and 10⁷ colony-forming units/ml., incubated in tryptose phosphate broth for 6 hr. at 37° C., separated from broth, reincubated for 18-24 hr. at 30°C, washed twice with aqueous 0.0743M potassium dihydrogen phosphate containing 0.1% of polyethylene glycol p-isooctylphenyl ether (Triton X-100 brand), and stored at -70°C The disks were thawed prior to testing.

In the test against transient microflora sterile excised porcine skin disks were inoculated with 20 μl of a freshly prepared culture of Klebsiella oxytoca K-1, Escherichia coli E-32, Pseudomonas aeruginosa Ps-4 (all from Bender Hygienic Laboratory, Albany, N.Y.) or Staphylococcus aureus ATCC 39881, then allowed to air dry for 15 min.

An inoculated disk was tested by immersing for 3 min. (resident microflora test) or 5 min. (transient microflora test) in 2 ml. of a 5 mM solution of the test compound in sterile distilled water or 25% aqueous dimethylsulfoxide or the solvent alone as a control solution, rinsing twice with sterile aqueous 25 mM potassium dihydrogen phosphate (pH 7.2), swirling for 30 sec. in tryptose phosphate broth modified to contain 0.8% polysorbate 80, 0.25% condensed naphthalene sulfonic acid sodium salt anionic dispersant (Tamol-N Micro brand), 0.1% lecithin and 0.1% sodium thiosulfate, and sampling.

To determine the number of surviving bacteria a sample was neutralized and 1.0 ml. aliquots of successive tenfold dilutions thereof in the modified tryptose phosphate broth were plated in duplicate with tryptic soy agar (DIFCO Laboratories, Detroit, Mich.) by the pour plate technique. The plates were incubated at 37°C for 48-72 hr. and counted using an automated colony counter coupled with a computer for statistical analysis of the data. Mean log reductions of counts from controls and standard errors were determined.

Table IV shows the results of the resident microflora test using Staphlococcus epidermidis ATCC 17917. Table V shows the results of the transient microflora test using all four test microorganisms. Standard errors for controls were in all cases ±0.15 or less.

TABLE IV
______________________________________
Resident Microflora Test
Mean Log
Example
Reduction
______________________________________
1Ab
0.51 ± 0.10
2a
1.05 ± 0.23
3a
0.44 ± 0.06
4a
0.53 ± 0.11
6a
1.26 ± 0.12
7b
0.57 ± 0.14
8b
0.56 ± 0.12
9a
0.77 ± 0.12
10a,c
0.88 ± 0.18
12b
0.29 ± 0.18
13b
0.72 ± 0.13
14b
0.48 ± 0.15
______________________________________
a sterile distilled water
b 25% aqueous dimethylsulfoxide
c 8 disks

TABLE V
______________________________________
Transient Microflora Test
Mean Log Reduction
Example
K. oxytoca E. coli   Ps. aerug.
S. aureus
______________________________________
1Ab
1.68 ± 0.26
1.20 ± 0.09
1.38 ± 0.12
1.21 ± 0.13
2a
2.49 ± 0.20
1.37 ± 0.13
1.99 ± 0.08
1.01 ± 0.20
3a
1.15 ± 0.36
1.07 ± 0.08
1.04 ± 0.06
0.87 ± 0.13
4a
2.12 ± 0.35
1.52 ± 0.12
1.72 ± 0.09
1.19 ± 0.13
5a
0.67 ± 0.14
e         e        e
6a
1.90 ± 0.33
0.98 ± 0.08
1.66 ± 0.08
0.96 ± 0.13
7b
1.65 ± 0.22c
1.13 ± 0.14
1.14 ± 0.13
1.32 ± 0.11
8b
1.11 ± 0.14d
1.11 ± 0.15
1.56 ± 0.04
1.39 ± 0.11
9a
1.98 ± 0.29
1.59 ± 0.14
1.62 ± 0.10
1.26 ± 0.20
10a
1.74 ± 0.19
1.32 ± 0.12
1.78 ± 0.11
1.36 ± 0.15
11b
0.59 ± 0.12
e         e        e
12b
0.78 ± 0.18
e         e        e
13b
1.34 ± 0.22
0.87 ± 0.07
1.22 ± 0.07
1.20 ± 0.11
14b
1.82 ± 0.36
1.21 ± 0.09
1.27 ± 0.10
0.88 ± 0.07
______________________________________
a sterile distilled water
b 25% aqueous dimethylsulfoxide
c 8 disks
d 9 disks
e not tested

As also stated above and in accordance with the third process aspect of the invention the compounds of Formulas I and II and the pharmaceutically acceptable acid addition salts thereof are most especially useful against pathogenic dental microbes and associated dental plaque and gingivitis in primates. This was demonostrated by tests in vitro against dental plaque forming bacteria and in vivo both prophylactically and therapeutically against plaque formation and gingival inflammation as manifestations of periodontal disease in the monkey.

In the in vitro dental plaque test Streptococcus mutans 6715-13 and Actinomyces viscosus M-100 were used as plaque-forming microorganisms. Cultures were stored prior to use in a frozen or lyophilized state and working stock cultures were maintained by twice monthly passage in fluid thioglycollate medium containing 20% (w/v) meat extract and excess calcium carbonate. For plaque formation a horse meat infusion medium containing 5% sucrose, 1% trypticase and 0.5% sodium chloride and having pH 7.1 (cf. Jordan et al., J. Dent. Res., vol. 39, pp. 116-123, 1960) was used. All cultures were adapted to this medium by at least one growth cycle prior to use in the test.

The test objects were clean, sterile ceramic hydroxylapatite (durapatite) slabs approximately 1 cm.×1cm.×1 mm. in size, which were suspended by nichrome wire in medium containing the plaque-forming microorganism. The slabs were transferred to medium not containing the plaque-forming microorganism on each of the next two days. Media were maintained at 37°C under an anaerobic atmosphere (85% N₂ /10% H₂ /5% CO₂). Slabs having plaques of similar size were used in each test.

A 1% (w/v) solution of each of the test compounds in 50% aqueous dimethylsulfoxide was prepared. This and four successive fivefold dilutions thereof in sterile distilled water (0.5%, 0.1%, 0.05%, 0.01%) were used as the test solutions.

A plaque-covered durapatite slab was immersed in 10 ml. of a test solution for 30 min. at 37°C, removed, twice rinsed by immersing in 15 ml. of sterile distilled water, then immersed in fresh medium containing the pH indicator bromocresol purple. Plaques were judged to be killed if acidity failed to form and turbidity failed to increase in the medium.

Table VI shows the results of this thirty-minute antiplaque test.

1-Methyl-4-methylaminopyridinium iodide (m.r. 224°-226°C) was prepared from 4-cyano-1-methylpyridinium iodide and methylamine as described by the above-cited Landquist reference, tested in the thirty-minute antiplaque test, and found to be inactive at the 0.5% concentration.

TABLE VI
______________________________________
Thirty-Minute Antiplaque Test
Minimum Plaque-Killing
Concentration (% w/v)
Example    S. mutans 6715-13
A. viscosus M-100
______________________________________
1A       0.01         0.01
2         0.05         0.05
3         0.1          0.05
4         0.05         0.05
5         0.05         0.05
6         0.05         0.1
7         0.05         0.05
8         0.05         0.05
9         0.05         0.05
10         0.05         0.05
11         0.05         0.01
12         0.05         0.05
13         0.05         0.05
14         0.05         0.05
15         0.05         0.05
16         0.05         0.05
17         0.05         0.05
18         0.01         0.01
19         0.05         0.05
20         0.1          0.05
21         0.01         0.01
22         0.01         0.01
23         0.05         0.05
24         0.01         0.01
______________________________________

To simulate a person's daily use of a dentifrice or a mouthwash containing a compound of Formula I or II or a pharmaceutically acceptable acid addition salt thereof the same test was conducted by immersing the plaque-containing slab in the test solution for two minutes daily for as many days up to five as necessary to kill the plaque. If the plaque was not killed in five days, the test compound was still considered active if a higher concentration thereof killed the plaque in five days or less.

The results of this daily two-minute anitplaque test are expressed as a plaque bactericidal index (PBI) calculated by the equation

PBI=concentration (mM)>2 (min.)×number of days and are set forth in Table VII. The PBI values for the compound of part A of Example 1, for example, were calculated as follows:

PBI=0.31 mM×2 min.×4 days=2.5.

The approximately twofold difference between the PBI values for the compound of part A of Example 1, which is a hydrobromide salt, and the compound of parts B and C of Example 1, which is a hydrochloride salt, is not considered significant and is consistent with the belief that the antimicrobial properties of the compounds of Formulas I and II are independent of the salt forms.

However, significant differences were shown in the daily two-minute antiplaque test between the compound of Example 1 and two prior art compounds. Table VII shows that the compounds of parts A, B, and C of Example 1 are from about 5 times to about 14 times more potent than the prior art compound of Example 19 in this test. Octenidine hydrochloride, which is the compound of parts A and B of Example 10 of above-cited U.S. Pat. No. 4,206,215, showed PBI values of 25.6 against S. mutans 6715-13 and 19.2 against A. viscosus M-100. The compounds of parts A, B and C of Example 1 are thus from about 8 times to about 18 times more potent than octenidine hydrochloride in the test.

The compounds of Examples 6 and 17 were not active in this test at concentrations of 6.32 mM and 5 mM, respectively, and were not tested at higher concentrations.

TABLE VII
______________________________________
Daily Two-Minute Antiplaque Test
Plaque Bactericidal Index (PBI)
Example    S. mutans 6715-13
A. viscosus M-100
______________________________________
1A         2.5          2.5
1B,C       1.4          1.4
2          8.0          5.4
3          10.4         5.2
4          7.8          7.8
5          13.3         13.3
7          12.5         12.5
8          10.0         10.0
9          8.4          10.4
10         10.8         13.5
11         10.0         10.0
12         9.7          9.7
13         20.0         20.0
14         10.4         10.4
15         30.0         12.0
16         15.4         10.3
18         5.4          5.4
19         12.4         19.2
20a   19.2         6.4
21a   4.6          3.0
22a   2.9          4.4
23a   12.8         6.4
24a   2.9          4.4
______________________________________
a When tested at the same time as these compounds the compound of
Example 1B showed a PBI value of 2.8 against both S. mutans 671513 and A.
viscosus M100.

Two tests of the compound of part A of Example 1 against plaque formation and gingival inflammation in the monkey were carried out, one prophylactic and the other therapeutic. Cynomolgus monkeys of both sexes having all of their permanent teeth and evidencing gingivitis were used, without pretreatment in the therapeutic test. In the prophylactic test the calculus and gingivitis were reduced by a combination of scaling and brushing with 0.2% aqueous chlorohexidine gluconate prior to treatment with the test compound. Three males and three females were used in each test group.

In each monkey the following four teeth and their associated gingival areas were examined quantitatively for plaque and gingivitis: maxillary right first molar (1:6), maxillary left first premolar (2:4), mandibular left first molar (3:6), mandibular right first premolar (4:4). Plaque was assessed on the following scale: 0, no plaque on probe; 1, plaque on probe; 2, visible plaque; 3, heavy plaque. Gingivitis was assessed on the following scale: 0, absence of inflammation; 1, mild inflammation; 2, moderate inflammation; 3, severe inflammation. A plaque sample was taken from each of two monkeys of each test group and assessed for the following morphologic groups: coccoid, straight rods, filaments, fusiforms, curved plus motile forms. The number of microorganisms of each morphologic group was expressed as a percentage of the total cell number counted.

Positioned face down and under sedation each monkey was treated with 5 ml. of an aqueous solution of the test compound or of water alone as a control. One fourth of the 5 ml. amount was delivered to each quadrant. The excess was allowed to drain from the monkey's mouth.

In the prophylactic test the test solutions were 0.32 mM and 0.64 mM aqueous solutions of the compound of part A of Example 1 and a 3.2 mM aqueous solution of octenidine hydrochloride. Each monkey was treated once daily with the test solution for five consecutive days a week for three consecutive weeks. Plaque and gingivitis were scored on days 7, 14 and 21. Plaque samples for morphologic examination were taken on days 10, 17 and 24.

In the therapeutic test the test solutions were a 0.64 mM aqueous solution of the compound of part A of Example 1, 3.2 mM aqueous octenidine hydrochloride and 3.2 mM aqueous chlorhexidine gluconate. The test solutions were delivered into the gingival sulcus. Each monkey was treated once daily with the test solution for five consecutive days a week for two consecutive weeks. Plaque and gingivitis were scored on days 0, 7 and 15. Plaque samples for morphologic examination were taken on days 0, 3 and 10.

The results for the prophylactic test are shown in Tables VIII-X. Table VIII shows plaque scores, which are expressed as means per tooth with standard errors. Table IX shows gingivitis scores, which are also expressed as means per tooth with standard errors. Table X shows plaque morphology, which is expressed as the combine percentages of filaments, fusiforms and curved plus motile forms as a percentage of total forms assessed. These three forms are associated with plaque. The results for the therapeutic test are similarly shown in Tables XI-XIII.

The results of the prophylactic test show that all three test solutions significantly retarded redevelopment of gingivitis during the test period, the compound of part A of Example 1 5-10 times more effectively than octenidine hydrochloride. The results of the therapeutic test show that only the compound of part A of Example 1 effected significant reduction of gingivitis during the test period. Octenidine hydrochloride or chlorhexidine gluconate did not significantly cause disease remission under the test protocol.

TABLE VIII
______________________________________
Prophylactic Test
Test       Mean Plaque Score
Solution   Day 7       Day 14    Day 21
______________________________________
Water      0.48 ± 0.17
1.05 ± 0.13
1.30 ± 0.15
Example 1A 0.49 ± 0.21
0.61 ± 0.21
0.94 ± 0.28
0.32 mM
Example lA 0.28 ± 0.11
0.69 ± 0.20
0.76 ± 0.19
0.64 mM
Octenidine 0.30 ± 0.08
0.42 ± 0.21
0.65 ± 0.21
Hydrochloride
3.2 mM
______________________________________

TABLE IX
______________________________________
Prophylactic Test
Test      Mean Gingivitis Score
Solution  Day 7       Day 14      Day 21
______________________________________
Water     0.42 ± 0.14
1.24 ± 0.09
1.82 ± 0.08
Example 1A
0.15 ± 0.015
0.40 ± 0.08
0.70 ± 0.12
0.32 mM
Example 1A
0.22 ± 0.08
0.46 ± 0.06
0.48 ± 0.08
0.64 mM
Octenidine
0.36 ± 0.05
0.58 ± 0.1
0.71 ± 0.14
Hydrochloride
3.2 mM
______________________________________

TABLE X
______________________________________
Prophylactic Test
Test      % Plaque-Associated Morphologic Forms
Solution  Day 10       Day 17     Day 24
______________________________________
Water     58.0 ± 2.3
68.4 ± 1.6
69 ± 1.8
Example 1A
42.6 ± 4.8
20.6 ± 1.2
24.5 ± 3.6
0.32 mM
Example 1A
13.6 ± 2.9
12.8 ± 3.6
25 ± 3.6
0.64 mM
Octenidine
27.5 ± 2.6
18.7 ± 2.9
24.6 ± 2.8
Hydrochloride
3.2 mM
______________________________________

TABLE XI
______________________________________
Therapeutic Test
Test      Mean Plaque Score
Solution  Day 0        Day 7     Day 15
______________________________________
Water     1.21 ± 0.69
1.65 ± 0.1
1.59 ± 0.56
Example 1A
1.53 ± 0.46
0.39 ± 0.26
0.42 ± 0.32
0.64 mM
Octenidine
1.36 ± 0.53
0.49 ± 0.29
0.46 ± 0.37
Hydrochloride
3.2 mM
Chlorhexidine
1.96 ± 0.57
0.94 ± 0.43
0.89 ± 0.50
Gluconate
3.2 mM
______________________________________

TABLE XII
______________________________________
Therapeutic Test
Test      Mean Gingivitis Score
Solution  Day 0        Day 7     Day 15
______________________________________
Water     1.74 ± 0.33
2.21 ± 0.16
2.19 ± 0.34
Example 1A
1.64 ± 0.14
1.08 ± 0.42
0.35 ± 0.16
Octenidine
1.79 ± 0.17
1.63 ± 0.18
1.36 ± 0.28
Hydrochloride
3.2 mM
Chlorhexidine
1.97 ± 0.25
1.65 ± 0.15
1.06 ± 0.68
Gluconate
3.2 mM
______________________________________

TABLE XIII
______________________________________
Therapeutic Test
Test      % Plaque-Associated Morphologic Forms
Solution  Day 0        Day 3     Day 10
______________________________________
Water     78.6 ± 3.6
58.7 ± 6.6
72.8 ± 5.3
Example 1A
79.7 ± 4.1
10.3 ± 3.7
10.5 ± 3.9
0.64 mM
Octenidine
77.3 ± 3.6
59.8 ± 4.6
38.2 ± 4.5
Hydrochloride
3.2 mM
Chlorhexidine
78.0 ± 4.3
38.5 ± 4.6
45.6 ± 3.2
Gluconate
3.2 mM
______________________________________

Method of Use and Compositions

The first and third process aspects of the invention, which are methods of use of a compound of Formula II or an acid addition salt thereof, are generally carried out using an antimicrobial composition thereof in accordance with the second composition of matter aspect of the invention.

In the methods of use living tissue includes plant and animal tissue and animal tissue includes human tissue, especially the tissues of the oral cavity. Nonliving surfaces include hard and soft surfaces, especially those located or used where prevention of microbial transmission is desired. Hard surfaces include those of building interiors, furniture and equipment. Soft surfaces include those of paper and cloth, wet or dry.

In the compositions a compatible vehicle is one which does not interfere with the antimicrobial effectiveness of the compound of Formula II and comprises a diluent and one or more pharmaceutical adjuncts including surfactants, thickeners, buffers, emollients, preservatives, dyes, pigments, perfumes, flavors and other ingredients depending on the purposes of the compositions. The compositions include tinctures, lotions, ointments, creams, jellies, powders, surgical scrubs, skin cleansers, shampoos, soaps, dentifrices, mouthwashes, household and industrial disinfectants and cleansers and protective coatings and are prepared by conventional methods.

The preferred diluent is an aqueous or aqueousalcoholic diluent. The preferred concentration of the compound of Formula II or the acid addition salt thereof is from about 0.01% to about 10% by weight/volume. Compositions of the compound of part C of Example 1 are particularly preferred, especially those for use in the oral cavity. The composition of Example 20 is such a composition.

EXAMPLE 20

______________________________________
Ingredient        % (Weight/Volume)
______________________________________
Compound of Example lC
0.025
Sorbitol          7.0
Alcohol USP       8.0
Glycerin          5.0
Poloxamer 237     0.5
Flavors           0.1
Dye               0.0001
Water to make     100.0
______________________________________

Claims

1. N-[1-(Alkyl or arylmethyl)-4(1H)-pyridinylidine]-alkanamine having the structural formula ##STR8## wherein R is alkyl having from 6 to 18 carbon atoms; and

R' is alkyl having from 2 to 12 carbon atoms, phenylmethyl or halophenylmethyl; or

except that R and R' cannot both be octyl; or

an acid addition salt thereof.

2. A compound according to claim 1 wherein R is alkyl having from 6 to 13 carbon atoms or an acid addition salt thereof.

3. A compound according to claim 2 wherein R' is alkyl having from 6 to 9 carbon atoms or an acid addition salt thereof.

4. A compound according to claim 2 wherein R' is phenylmethyl or 4-chlorophenylmethyl or an acid addition salt thereof.

5. The method of reducing the number of microbes on a living tissue or a nonliving surface which comprises applying to the tissue or surface an antimicrobially effective amount of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine having the structural formula ##STR9## wherein R is alkyl having from 6 to 18 carbon atoms; and

R" is alkyl having from 1 to 12 carbon atoms, phenylmethyl or halophenylmethyl;

or an acid addition salt thereof.

6. The method according to claim 5 wherein R is alkyl having from 6 to 13 carbon atoms.

7. The method according to claim 6 wherein R" is alkyl having from 1 to 9 carbon atoms.

8. The method according to claim 6 wherein R" is phenylmethyl or 4-chlorophenylmethyl.

9. The method of reducing the number of pathogenic dental microbes and associated dental plaque and gingivitis in a primate which comprises applying to the oral cavity of the primate an antimicrobially effective amount of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine having the structural formula ##STR10## or a pharmaceutically acceptable acid addition salt thereof wherein

R is alkyl having from 6 to 18 carbon atoms; and

R" is alkyl having from 1 to 12 carbon atoms, phenylmethyl or halophenylmethyl;

except that R and R" cannot both be octyl.

10. The method according to claim 9 wherein R is alkyl having from 7 to 13 carbon atoms.

11. The method according to claim 10 wherein R" is alkyl having from 1 to 9 carbon atoms.

12. The method according to claim 10 wherein R" is phenylmethyl or 4-chlorophenylmethyl.

13. An antimicrobial composition which comprises an antimicrobially effective concentration of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkanamine having the structural formula ##STR11## or a pharmaceutically acceptable acid addition salt thereof and a compatible vehicle consisting of a diluent and one or more pharmaceutical adjuncts

wherein

R is alkyl having from 6 to 18 carbon atoms; and

R" is alkyl having from 1 to 12 carbon atoms, phenylmethyl or halophenylmethyl;

except that R and R" cannot both be octyl.

14. A composition according to claim 13 wherein the concentration of N-[1-(alkyl or arylmethyl)-4(1H)-pyridinylidine]alkane or a pharmaceutically acceptable acid addition salt thereof is from about 0.01% to about 10% by weight/volume.

15. A composition according to claim 14, wherein the diluent is an aqueous or aqueous-alcoholic diluent.

16. A compound selected from the group consisting of N-(1-octyl-4(1H)-pyridinylidine)hexanamine having the structural formula ##STR12## N-(1-nonyl-4(1H)-pyridinylidine)hexanamine having the structural formula ##STR13## and N-(1-hexyl-4(1H)-pyridinylidine)nonanamine having the structural formula ##STR14## and the acid addition salts thereof.

17. N-(1-Octyl-4(1H)-pyridinylidine)hexanamine monohydrochloride according to claim 16.

18. N-(1-Nonyl-4(1H)-pyridinylidine)hexanamine monohydrochloride according to claim 16.

19. N-(1-Hexyl)-4(1H)-pyridinylidine)nonanamine monohydrochloride according to claim 16.

20. The method of reducing the number of microbes on a living tissue or a nonliving surface which comprises applying to the tissue or surface an antimicrobially effective amount of a compound according to claim 16.

21. The method of reducing the number of pathogenic dental microbes and associated dental plaque and gingivitis in a primate which comprises applying to the oral cavity of the primate an antimicrobially effective amount of a compound according to claim 16.

22. An antimicrobial composition which comprises an antimicrobially effective concentration of a compound according to claim 16 and a compatible vehicle consisting of a diluent and one or more pharmaceutical adjuncts.